Java LinkedBlockingDeque offerFirst()用法及代码示例

LinkedBlockingDeque的offerFirst(E e)方法将在参数中传递的元素插入Deque容器的前面。如果超出了容器的容量，则不会像add()和addFirst()函数一样返回异常。

用法:

public boolean offer(E e)

参数：此方法接受强制参数e，该参数是要在LinkedBlockingDeque的前面插入的元素。

返回值：如果已插入元素，则此方法返回true，否则返回false。

以下示例程序旨在说明LinkedBlockingDeque的offerFirst()方法：

示例1:

// Java Program Demonstrate offerFirst() 
// method of LinkedBlockingDeque 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<Integer> LBD 
            = new LinkedBlockingDeque<Integer>(4); 
  
        // Add numbers to end of LinkedBlockingDeque 
        LBD.offerFirst(7855642); 
        LBD.offerFirst(35658786); 
        LBD.offerFirst(5278367); 
        LBD.offerFirst(74381793); 
  
        // Cannot be inserted 
        LBD.offerFirst(10); 
  
        // cannot be inserted hence returns false 
        if (!LBD.offerFirst(10)) 
            System.out.println("The element 10 cannot be inserted"+ 
                                           " as capacity is full"); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
    } 
}

输出：

The element 10 cannot be inserted as capacity is full
Linked Blocking Deque: [74381793, 5278367, 35658786, 7855642]

示例2:

// Java Program Demonstrate offerFirst() 
// method of LinkedBlockingDeque 
  
import java.util.concurrent.LinkedBlockingDeque; 
import java.util.*; 
  
public class GFG { 
    public static void main(String[] args) 
        throws IllegalStateException 
    { 
  
        // create object of LinkedBlockingDeque 
        LinkedBlockingDeque<String> LBD 
            = new LinkedBlockingDeque<String>(4); 
  
        // Add numbers to end of LinkedBlockingDeque 
        LBD.offerFirst("abc"); 
        LBD.offerFirst("gopu"); 
        LBD.offerFirst("geeks"); 
        LBD.offerFirst("richik"); 
  
        // Cannot be inserted 
        LBD.offerFirst("hii"); 
  
        // cannot be inserted hence returns false 
        if (!LBD.offerFirst("hii")) 
            System.out.println("The element 'hii' cannot be"
                           +" inserted as capacity is full"); 
  
        // before removing print queue 
        System.out.println("Linked Blocking Deque: " + LBD); 
    } 
}

输出：

The element 'hii' cannot be inserted as capacity is full
Linked Blocking Deque: [richik, geeks, gopu, abc]

参考： https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/LinkedBlockingDeque.html#offerFirst(E)

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注：本文由纯净天空筛选整理自gopaldave大神的英文原创作品 LinkedBlockingDeque offerFirst() method in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。